org.apache.druid.query

Class JoinDataSource

java.lang.Object

org.apache.druid.query.JoinDataSource

All Implemented Interfaces:

DataSource

public class JoinDataSource
extends Object
implements DataSource

Represents a join of two datasources. Logically, this datasource contains the result of: (1) prefixing all right-side columns with "rightPrefix" (2) then, joining the left and (prefixed) right sides using the provided type and condition Any columns from the left-hand side that start with "rightPrefix", and are at least one character longer than the prefix, will be shadowed. It is up to the caller to ensure that no important columns are shadowed by the chosen prefix. When analyzed by DataSourceAnalysis, the right-hand side of this datasource will become a PreJoinableClause object.

Method Summary

Modifier and Type	Method and Description
static JoinDataSource	create(DataSource left, DataSource right, String rightPrefix, String condition, JoinType joinType, ExprMacroTable macroTable)
boolean	equals(Object o)
List<DataSource>	getChildren() Returns datasources that this datasource depends on.
String	getCondition()
JoinConditionAnalysis	getConditionAnalysis()
JoinType	getJoinType()
DataSource	getLeft()
DataSource	getRight()
String	getRightPrefix()
Set<String>	getTableNames() Returns the names of all table datasources involved in this query.
int	hashCode()
boolean	isCacheable() Returns true if queries on this dataSource are cacheable at both the result level and per-segment level.
boolean	isConcrete() Returns true if this datasource represents concrete data that can be scanned via a Segment adapter of some kind.
boolean	isGlobal() Returns true if all servers have a full copy of this datasource.
String	toString()
DataSource	withChildren(List<DataSource> children) Return a new DataSource, identical to this one, with different children.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

create

public static JoinDataSource create(DataSource left,
                                    DataSource right,
                                    String rightPrefix,
                                    String condition,
                                    JoinType joinType,
                                    ExprMacroTable macroTable)

getTableNames

public Set<String> getTableNames()

Description copied from interface: DataSource

Returns the names of all table datasources involved in this query. Does not include names for non-tables, like lookups or inline datasources.

Specified by:

getTableNames in interface DataSource

getLeft

public DataSource getLeft()

getRight

public DataSource getRight()

getRightPrefix

public String getRightPrefix()

getCondition

public String getCondition()

getConditionAnalysis

public JoinConditionAnalysis getConditionAnalysis()

getJoinType

public JoinType getJoinType()

getChildren

public List<DataSource> getChildren()

Description copied from interface: DataSource

Returns datasources that this datasource depends on. Will be empty for leaf datasources like 'table'.

Specified by:

getChildren in interface DataSource

withChildren

public DataSource withChildren(List<DataSource> children)

Description copied from interface: DataSource

Return a new DataSource, identical to this one, with different children. The number of children must be equal to the number of children that this datasource already has.

Specified by:

withChildren in interface DataSource

isCacheable

public boolean isCacheable()

Description copied from interface: DataSource

Returns true if queries on this dataSource are cacheable at both the result level and per-segment level. Currently, dataSources that modify the behavior of per-segment processing are not cacheable (like 'join'). Nor are dataSources that do not actually reference segments (like 'inline'), since cache keys are always based on segment identifiers. Note: Ideally, queries on 'join' datasources _would_ be cacheable, but we cannot currently do this due to lacking the code necessary to compute cache keys properly.

Specified by:

isCacheable in interface DataSource

isGlobal

public boolean isGlobal()

Description copied from interface: DataSource

Returns true if all servers have a full copy of this datasource. True for things like inline, lookup, etc, or for queries of those. Currently this is coupled with joinability - if this returns true then the query engine expects there exists a JoinableFactory which might build a Joinable for this datasource directly. If a subquery 'inline' join is required to join this datasource on the right hand side, then this value must be false for now. In the future, instead of directly using this method, the query planner and engine should consider JoinableFactory.isDirectlyJoinable(DataSource) when determining if the right hand side is directly joinable, which would allow decoupling this property from joins.

Specified by:

isGlobal in interface DataSource

isConcrete

public boolean isConcrete()

Description copied from interface: DataSource

Returns true if this datasource represents concrete data that can be scanned via a Segment adapter of some kind. True for e.g. 'table' but not for 'query' or 'join'.

Specified by:

isConcrete in interface DataSource

See Also:

which uses this, which uses this

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object